The invention relates generally to messaging between host processors and/or processes.
An increasing number of powerful data storage systems are becoming commercially available. These systems are capable of storing and rapidly accessing hundreds of gigabytes, even terabytes, of data. The Symmetrix 3XXX and 5XXX Series data storage systems that are sold by EMC, Corp. of Hopkinton, Mass. are good examples of these new, high performance data storage systems. The Symmetrix data storage systems, which are frequently used for online transaction processing and other response-intensive applications, are part of a group of data storage systems that are more generally referred to as integrated cached disk array systems. Such systems include a large array of small disk storage devices and a large cache memory. For example, in the disk array there may be as many as 128 5.24 inch disk storage devices each with its own cache buffer and the total cache can be above 4 Gigabytes. The cache is made up of high speed storage units which collectively are used as an intermediary between the host processors that are connected to the data storage system and the internal storage disks of the disk array. Internally, a plurality of microprocessors (e.g. up to 144 individual microprocessors) handle accesses to the cache and the disks of the disk array. Thus, a high degree of parallelism and thus efficiency is possible in processing I/O tasks.
These systems are based on the principle that currently active data at any given time is relatively small in comparison to the total amount of data that is stored in the system and thus the currently active data is stored in the cache where it can be accessed very quickly. Because access times for reading and writing to cache are much shorter than for disks, storing active data in cache memory results in a substantial improvement in performance.
Such systems use various other techniques to enhance performance and reliability. For example, in the Symmetrix data storage systems, the cache has a separate power supply with battery backup so that a power failure to the main system will not result in loss of data in the cache. Also those systems include a mirroring facility to generate a duplicate of all stored data. In accordance with mirroring, the data storage system generates two copies of data in the disk array, each copy on a different set of the disks. When writes occur to data in the system, both copies are updated. Thus, if one disk fails wiping out all of the data stored on that disk, a duplicate of that data can be found and accessed on another disk.
Today's data storage systems, exemplified by the Symmetrix data storage systems of EMC, Corp., make possible further advances in overall system design and performance, such as the present invention described below.